Renewable energy sources and sources of chemicals for use in polymers are of increasing importance. They are a means of reducing dependence on imported oil and provide a substitute for fossil fuels. Fossil fuels are also a principal source of materials for basic chemical constituents to be used in other industries, such as chemical monomers for the making of polymers. Biomass is a renewable resource that can provide some of the needs for sources of chemicals and fuels. Part of the challenge of biomass utilization is the efficient recovery of the basic chemical constituents.
Biomass includes, but is not limited to, plant parts, fruits, vegetables, plant processing waste, wood chips, chaff, grain, grasses, corn, corn husks, weeds, aquatic plants, hay, paper, paper products, recycled paper and paper products, and any cellulose containing biological material or material of biological origin. The economics depend on the ability to produce large amounts of biomass on marginal land, or in a water environment where there are few or no other significantly competing economic uses of that land or water environment. The economics can also depend on the disposal of biomass that would normally be placed in a landfill.
The growing, harvesting and processing of biomass in a water environment provides a space where there is plenty of sunlight and nutrients while not detracting from more productive alternate uses. In addition, biomass contributes to the removal of carbon dioxide from the atmosphere as the biomass grows. The use of biomass can be one process for recycling atmospheric carbon while producing fuels and chemical precursors. Biomass when heated in an environment with low or no oxygen will generate a liquid product known as pyrolysis oil. Biomass also contains a significant amount of lignin, which contains a substantial amount of material that can be used as precursors for chemical and fuels. The lignin structure contains aromatic rings that are linked together through carbon-carbon bonds and through carbon-oxygen bonds. The compounds that have high value are the alkyl-benzene compounds and phenolic compounds that can be recovered from the biomass.
One of ways to convert lignin to fuels or chemicals is by base catalyzed depolymerization followed by hydrotreating, as shown in U.S. Patent publications 2003/0100807A1 and 2003/0115792A1. This process uses a strong base to partially break up the lignin compounds. One major problem of this approach is high consumption of strong base such as NaOH which makes it not very attractive from economic stand point of view. Our recent study showed that final pH of reaction product need to be above 12.4 in order to have high lignin conversion. This makes the use of low cost basic materials such as boiler ashes impractical.
Processes that avoid this need for strong bases can shift the recovery of organic precursors from biomass to economically viable processes, as well as lessen the cost of environmental protection for bio-conversion processes.